Wireless communication technology is progressing every day and accompanying that progress, various mobile telephone formats have appeared, including second-generation mobile phone formats, third-generation mobile phone formats and 3.9-generation mobile phone formats.
Second-generation mobile formats include the GSM (Global System for Mobile communications) format, the IS-95 format and the PDC (Personal Digital Cellular) format.
Diversity reception technology, which is one type of wireless communication technology, has been practically used in mobile phone handsets using the GSM format and the IS-95 format. In addition, diversity reception technology in the PDC format is disclosed in Japanese Patent No. 3101437.
Diversity reception technology includes (1) antenna diversity technology where an antenna with a high reception level is selected from a plurality of antennas, and (2) synthesis diversity technology where optimum data is decoded by synthesizing or switching received signals on the strength and phase of signals received from a plurality of antennas.
On the other hand, MIMO (Multi Input Multi Output) technology which is equipped with a plurality of antennas for both the sending side and the receiving side and which accomplishes high-speed, large-volume information transmissions has been practically used in wireless communications devices on the wireless LAN (Local Area Network) 802.11n format.
Among the third generation mobile phone formats are the W-CDMA (Wide-Band Code Division Multiplex Access) format and cdma 2000-1x. With the W-CDMA format or cdma 2000-1x, handover technology has been commercialized for moving between base stations without interrupting communications.
Handover technology that determines the magnitude of the reception level and hands over communications from a cell of a base station capable of sending and receiving the signal to a cell of another base station is disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2009-111644.
Among 3.9-generation mobile phone formats is the LTE (Long Term Evolution) format. With the LTE format, MIMO technology using four receiving antennas is employed and handover technology is also standardized.
There is an LTE-GSM dual mode transceiver that supports both the LTE format and the GSM format. With an LTE-GSM dual mode transceiver, when for example a mobile phone existing in a cell of a first base station using the LTE format is handed over to a cell of a second base station using the GSM format, it is necessary to accurately monitor the reception level of the signal received from the second base station.
However, the diversity reception technology disclosed in Japanese Patent No. 3101437 and the handover technology disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2009-111644 cannot accurately monitor the reception level of signals received from a first base station and a second base station with differing wireless formats.
In consideration of the foregoing, it is an exemplary object of the present invention to provide a wireless communications device that can monitor the reception level of signals received from a plurality of base stations with differing wireless formats, and a method and program for determining reception levels in the wireless communications device.